The present invention relates generally to semiconductor sensor devices and more particularly to methods of assembling semiconductor pressure sensor devices.
Semiconductor sensor devices, such as pressure sensors, are well known. Such devices use semiconductor pressure-sensing dies to sense the ambient atmospheric pressure. These dies are susceptible to mechanical damage during packaging and environmental damage when in use, and thus they must be carefully packaged. Further, pressure-sensing dies, such as piezo resistive transducers (PRTs) and parameterized layout cells (P-cells), do not allow full encapsulation because that would impede their functionality.
FIG. 1 shows a cross-sectional side view of a conventional packaged semiconductor sensor device 100. The semiconductor sensor device 100 has a pre-molded lead frame 102 comprising a metal die paddle 104 (also known as a lead frame flag), a plurality of metal lead fingers 106 that surround the die paddle 104, and molding compound 108. The molding compound 108 (i) fills areas between adjacent ones of the lead fingers 106 and between the lead fingers 106 and the die paddle 104, and (ii) forms a cavity 110 over the die paddle 104.
A P-cell 112 and a micro-control unit die (MCU) 114 are mounted on the die paddle 104 using a die-attach adhesive 116. The P-cell 112 and MCU 114 are electrically connected to one another and to the lead fingers 106 with bond wires 118. The P-cell 112 and MCU 114 then are encapsulated in a pressure-sensitive gel material 120, which enables the pressure of the ambient atmosphere to reach the pressure-sensing active region on the top side of the P-cell 112, while protecting the dies 112 and 114 and the bond wires 118 from mechanical damage during packaging and environmental damage (e.g., contamination and/or corrosion) when in use. The lead frame cavity 110 is covered by a lid 122, which has a vent hole 124 formed therethrough to expose the gel-covered P-cell 112 to ambient atmospheric pressure outside the sensor device 100.
One problem with the sensor device 100 is the high manufacturing cost due to the use of a pre-molded lead frame 102. Accordingly, it would be desirable to be able to assemble a pressure sensor device without the need for a pre-molded lead frame.